Graduate Thesis Or Dissertation

 

The effects of light on photosynthesis and rooting of leafy cuttings of Pisum sativum L. Public Deposited

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  • The effects of light incident on leafy cuttings is quite complex because' light influences several factors which may affect root formation. One effect of light is to influence the carbohydrate status of the cutting by influencing photosynthesis. The role of current photosynthate in the rooting of leafy cuttings is uncertain. Accordingly I investigated the extent to which the supply of current photosynthate influences root formation on leafy cuttings of Pisum sativum L. When net photosynthesis was reduced to zero by maintaining the cuttings at the C0₂ compensation point or by blocking CO₂ exchange with an antitranspirant, rooting was reduced to about 50% of the controls. In addition to reducing rooting these treatments significantly reduced sucrose and glucose levels in the basal portion of the cuttings compared to controls. These experiments suggest that the supply of current photo- synthate can limit root formation. The above conclusions were supported by experiments using different photosynthetic photon flux densities and photoperiod lengths during rooting. Defoliation experiments also supported the role of current photosynthate in root formation. Defoliation of cuttings reduced rooting and carbohydrate levels in the base of the cuttings. Light incident on defoliated stems increased rooting and sucrose levels in the base of the stems. Dipping the defoliated cuttings in an antitranspirant blocked CO₂ fixation and almost completely inhibited root formation. These data suggest that stem photosynthesis also contributed to root formation. These experiments suggest that one of the major effects of light incident on leafy pea cuttings is to influence the amount of photosynthate available for root formation. It is difficult to establish whether current photosynthate influences rooting directly or indirectly by affecting some other factor(s) which control rooting. Whatever the case, treatments which influence photosynthesis influence rooting in a parallel manner.
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